1. Field of the Invention
The present invention relates to home audio systems. More specifically it relates to a parametric equalizer to compensate for room modes.
2. Description of the Related Art
To enjoy music, many people set up listening rooms in their homes. Ideally, a room is specifically designed for to be a listening room at the time the home is built. However, most people do not have the luxury of a custom designed, dedicated listening room. For most people the listening room is retrofit into an existing home. Often by using an existing room. Further, the room designated to be the listening room often serves many purposes such as the family room, den or an office in addition to being a listening room.
High-end speakers and audio components have the capability of providing a near flat response through the audible range (about 20 Hz to 20 KHz). However, because most listening rooms were not designed specifically for this purpose and because these rooms are often multifunctional, the capabilities of the audio components often exceed those of the listening environment.
The sound interacts with the walls; parallel walls in particular are especially problematic, windows, doorways, and furniture. When the listening room was not designed with audio in mind, undesirable peaks and dead areas often result.
Retrofitting a listening room into an existing room of a house often means living with the existing room plan—including doorways, windows, walls and ceiling. Further, because the room may serve many functions, the listener may be further constrained in the selection of surface coverings, furniture materials, furniture location and/or speaker location.
Most rooms are designed with parallel surfaces—walls, floor, and ceiling. Given the size of a room in a typical home, usually less than 35 feet, the significant problems caused by the room dimensions are in the bass range. Thus, there is a need for a system corrects for undesirable peaks in the base frequencies.
Most prior art systems are digital. The problem with digital filters is two-fold. First, the filters required for this type of application are very long convolution filters in the digital domain and lead to a variety of artifacts that are not desirable for high-end home enthusiasts. Second, some formats, including vinyl, super audio CD (SACD) and DVD-A are extremely high resolution and suffer in quality drastically when converted into the digital domain and then back out into analog. There is a need for a system that corrects for undesirable peaks in the base frequencies while being transparent in the audio system. There is a need for a system that preserves the purity of analog recordings.
One prior art system is a digital room compensation system that attempts to deal with room modes and with other unwanted aspects including high frequency filtering and phase alignment. However, because it is digital system does not preserve the purity of an analog recording and thus is not desirable.
Another prior art system uses a pre-amplifier with some digital room correction circuitry. However, it does not fully address the problem caused by room modes.
Another prior art system utilizes an analog equalizer that has fixed Q (widths) and variable center frequencies. Different number of center frequencies may be adjusted for. However, the device is noisy. The addition of noise is undesirable in a listening room.
Another prior art system uses a single channel filter. A single channel of correction is inadequate to address problems caused by room modes.
None of the prior art systems are full parametric systems. None of the prior art systems allow for continuous fine adjustment of the width of the curve. There is a need for a fully parametric system that allows for continuous fine adjustments of the width of the curve.
There is a need for an analog based, parametric notch filtration system with at least two-channels, that has enough bands, bandwidth, attenuation, and flexibility to accurately address room mode problems. Further, there is a need for a system that allows continuous fine adjustment of attenuation and bandwidth.
To accurately correct for room mode problems, it is important to being able to measure, evaluate, and calculate what variables need to be used to correct the room mode issue. Since nearly every room is different, the variables used will be different.